I've had coastlocks open up more than once in the past . Since then, it's been tying direct. Until I found breakaways which have been reliable so far but I only use them for convinence sometimes.
I don't think the problems with coastlocks are that a fish bites down on them. During a fight fish can roll, dig in, twist and do all kinds of unruly things to your rig. At some point the lock can pop open (or hooks open up
). The same stuff happens with sharks sometimes.